last minute cramming calculus question

[Semidevil]

so I have a final in a few hours, but there is this darn problem that I have no idea how to do.

This is calc II, integration.....

how do you integrate an absolute value? is there a rule? I just don't know, having the absolute value signs....

lets say if I give you the integral from 0 to 3 of absolute value (3x - 5), how would you do it?? Can I just integrate and ignore the absolute value? probably not....

what's the rule for absolute value integration??

 

[gopunk]

you find which regions are negative and which are positive

or something like that... this was a few years ago.

so for your example, the turning point is 5/3. anything greater will put a positive value in the abs, and anything less will put negative.

and then I THINK you do intergrals for both. so like if what is inside will be negative, you would take the integral of -f(x) for 0 to 5/3, and the intergral of f(x) for 5/3 to 3 and add them

or perhaps you subtract.... ugh lemme look this up it's killing me

ahah i was right, you add them.
http://www.ltcconline.net/greenl/courses/116/IntegrationApps/fstfun19.gif

 

[DigDug]

may I never need to do math again.


I am very good at it, mind you. But I can't fvcking stand it.

 

[Turin39789]

Originally posted by: BlipBlop
may I never need to do math again.


I am very good at it, mind you. But I can't fvcking stand it.

what he said

 

[TurtleMan]

41/6 ....


i felt empowered by owning a ti92plus ...
there is nothing ti92+ can't do ...


damn gopunk... thank you for showing that sh!t..
it was bugging me as hell too ...
took calc like 3 yrs ago, can't remember jack..

 

[m0ti]

Yes finding regions is one way.

Other way is to do abs(x) = sqrt(x^2)

So replace your absolute value and then do the integral.

 

[vtqanh]

Originally posted by: Semidevil
so I have a final in a few hours, but there is this darn problem that I have no idea how to do.

This is calc II, integration.....

how do you integrate an absolute value? is there a rule? I just don't know, having the absolute value signs....

lets say if I give you the integral from 0 to 3 of absolute value (3x - 5), how would you do it?? Can I just integrate and ignore the absolute value? probably not....

what's the rule for absolute value integration??

When x <=5/3 : |3x-5| = -3x +5
When x >=5/3 : |3x-5| = 3x - 5

Integral |3x-5| from 0 to 3 = Integral of -3x+5 from 0 to 5/3 + Integral of 3x - 5 from 5/3 to 3
that's it